It is known to provide thermal insulation for bathtubs, whirlpool baths or spas, as shown in U.S. Pat. No. 5,345,621 issued in 1994, inventor D. R. Livingston. The purpose of this insulation is to prevent the water temperature inside the tub, during use, from dropping too fast, which alternately requires the tub to be filled again with warmer water if no heater is provided, or the heater to spend more energy heating the water, if a heater is provided.
The Livingston patent shows that the bathtub shell comprises a rigid fiberglass layer, provided on its interior surface with a smooth acrylic coating, and on its outer surface with an urethane foam insulation layer. The tub is installed in a wood skirt or podium structure, which spacedly surrounds the shell and on which the shell upper downturned peripheral edge rests. Livingston also discloses the use of an insulation blanket 30 which, as shown in FIG. 3 of the Livingston patent, forms an inverted dome to completely enclose the shell, spacedly therefrom. Thus, an air pocket is formed between the shell and the insulating blanket which promotes enhanced insulation for the whirlpool tub.
The insulating blanket of the Livingston patent is made from a multiple-layer plastic film (e.g. including air bubbles therein), provided with a sheet of aluminum or the like reflective metallic foil on the inner surface thereof, in spaced facing register with the urethane foam coating of the tub shell. It is known that the metallic foil will promote reflection of the heat irradiating from the tub back towards the tub.
A problem with the spa disclosed in the Livingston patent, is that its single insulating air pocket is not sufficient to prevent significant temperature loss of the water. indeed, the urethane foam layer is not efficient enough to prevent the water from loosing its energy therethrough, and even the insulating blanket is not efficient enough to prevent the water temperature to drop at a significant rate at room temperature. Furthermore, the Livingston tub provides a fluid-tight air pocket between the tub shell and the insulating blanket which, under the important temperature gradients present on one side of this air pocket in the tub water and on the other side of this air pocket in the ambient air, will promote important condensation and humidity accumulation in the air pocket. This high humidity percentage and condensation in this pocket is likely to result in mould formation, and the urethane foam is effectively likely to degenerate and rot over time, thus becoming less efficient, in addition to any hygiene problems which may result therefrom.
A further problem with prior art whirlpool tubs such as the Livingston tub, is that the noise emitted by the whirlpool tub, with its water pump, is at a high level.
It is noted that the problems noted hereinabove, occur not only in whirlpool bathtubs, but also in spas, ordinary bathtubs, shower stalls, therapeutic tubs, and the like.
The so-called therapeutic tubs are similar to whirlpool bathtubs, but include air jets injected in the water, instead of water jets. Some tubs combine both water and air jets. Throughout the present specification, reference will be made to sanitary devices as including all of the above-mentioned devices.